Cardiac disease treatment and device

ABSTRACT

A jacket of biological compatible material has an internal volume dimensioned for an apex of the heart to be inserted into the volume and for the jacket to be slipped over the heart. The jacket has a longitudinal dimension between upper and lower ends sufficient for the jacket to surround a lower portion of the heart with the jacket surrounding a valvular annulus of the heart and further surrounding the lower portion to cover at least the ventricular lower extremities of the heart. The jacket is adapted to be secured to the heart with the jacket surrounding at least the valvular annulus and the ventricular lower extremities. The jacket is adjustable on the heart to snugly conform to an external geometry of the heart and assume a maximum adjusted volume for the jacket to constrain circumferential expansion of the heart beyond the maximum adjusted volume during diastole and to permit unimpeded contraction of the heart during systole.

I. BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention pertains to a device and method fortreating heart disease. More particularly, the present invention isdirected to a method and device for treating congestive heart diseaseand related valvular dysfunction.

[0003] 2. Description of the Prior Art

[0004] Congestive heart disease is a progressive and debilitatingillness. The disease is characterized by a progressive enlargement ofthe heart.

[0005] As the heart enlarges, the heart is performing an increasingamount of work in order to pump blood each heart beat. In time, theheart becomes so enlarged the heart cannot adequately supply blood. Anafflicted patient is fatigued, unable to perform even simple exertingtasks and experiences pain and discomfort. Further, as the heartenlarges, the internal heart valves cannot adequately close. Thisimpairs the function of the valves and further reduces the heart'sability to supply blood.

[0006] Causes of congestive heart disease are not fully known. Incertain instances, congestive heart disease may result from viralinfections. In such cases, the heart may enlarge to such an extent thatthe adverse consequences of heart enlargement continue after the viralinfection has passed and the disease continues its progressivelydebilitating course.

[0007] Patients suffering from congestive heart disease are commonlygrouped into four classes (i.e., Classes I, II, III and IV). In theearly stages (e.g., Classes I and II), drug therapy is the commonlyproscribed treatment. Drug therapy treats the symptoms of the diseaseand may slow the progression of the disease. Importantly, there is nocure for congestive heart disease. Even with drug therapy, the diseasewill progress. Further, the drugs may have adverse side effects.

[0008] Presently, the only permanent treatment for congestive heartdisease is heart transplant. To qualify, a patient must be in the laterstage of the disease (e.g., Classes III and IV with Class IV patientsgiven priority for transplant). Such patients are extremely sickindividuals. Class III patients have marked physical activitylimitations and Class IV patients are symptomatic even at rest.

[0009] Due to the absence of effective intermediate treatment betweendrug therapy and heart transplant, Class III and IV patients will havesuffered terribly before qualifying for heart transplant. Further, aftersuch suffering, the available treatment is unsatisfactory. Hearttransplant procedures are very risky, extremely invasive and expensiveand only shortly extend a patient's life. For example, prior totransplant, a Class IV patient may have a life expectancy of 6 months toone-year. Heart transplant may improve the expectancy to about fiveyears.

[0010] Unfortunately, not enough hearts are available for transplant tomeet the needs of congestive heart disease patients. In the UnitedStates, in excess of 35,000 transplant candidates compete for only about2,000 transplants per year. A transplant waiting list is about 8-12months long on average and frequently a patient may have to wait about1-2 years for a donor heart. While the availability of donor hearts hashistorically increased, the rate of increase is slowing dramatically.Even if the risks and expense of heart transplant could be tolerated,this treatment option is becoming increasingly unavailable. Further,many patient's do not qualify for heart transplant for failure to meetany one of a number of qualifying criteria.

[0011] Congestive heart failure has an enormous societal impact. In theUnited States alone, about five million people suffer from the disease(Classes I through IV combined). Alarmingly, congestive heart failure isone of the most rapidly accelerating diseases (about 400,000 newpatients in the United States each year). Economic costs of the diseasehave been estimated at $38 billion annually.

[0012] Not surprising, substantial effort has been made to findalternative treatments for congestive heart disease. Recently, a newsurgical procedure has been developed. Referred to as the Batistaprocedure, the surgical technique includes dissecting and removingportions of the heart in order to reduce heart volume. This is a radicalnew and experimental procedure subject to substantial controversy.Furthermore, the procedure is highly invasive, risky and expensive andcommonly includes other expensive procedures (such as a concurrent heartvalve replacement). Also, the treatment is limited to Class IV patientsand, accordingly, provides no hope to patients facing ineffective drugtreatment prior to Class IV. Finally, if the procedure fails, emergencyheart transplant is the only available option.

[0013] Clearly, there is a need for alternative treatments applicable toboth early and later stages of the disease to either stop theprogressive nature of the disease or more drastically slow theprogressive nature of congestive heart disease. Unfortunately, currentlydeveloped options are experimental, costly and problematic.

[0014] Cardiomyoplasty is a recently developed treatment for earlierstage congestive heart disease (e.g., as early as Class III dilatedcardiomyopathy). In this procedure, the latissimus dorsi muscle (takenfrom the patient's shoulder) is wrapped around the heart and chronicallypaced synchronously with ventricular systole. Pacing of the muscleresults in muscle contraction to assist the contraction of the heartduring systole.

[0015] While cardiomyoplasty has resulted in symptomatic improvement,the nature of the improvement is not understood. For example, one studyhas suggested the benefits of cardiomyoplasty are derived less fromactive systolic assist than from remodeling, perhaps because of anexternal elastic constraint. The study suggests an elastic constraint(i.e., a non-stimulated muscle wrap or an artificial elastic sock placedaround the heart) could provide similar benefits. Kass et al., ReverseRemodeling From Cardiomyoplasty In Human Heart Failure: ExternalConstraint Versus Active Assist, 91 Circulation 2314-2318 (1995).

[0016] Even though cardiomyoplasty has demonstrated symptomaticimprovement, studies suggest the procedure only minimally improvescardiac performance. The procedure is highly invasive requiringharvesting a patient's muscle and an open chest approach (i.e.,sternotomy) to access the heart. Furthermore, the procedure isexpensive—especially those using a paced muscle. Such procedures requirecostly pacemakers. The cardiomyoplasty procedure is complicated. Forexample, it is difficult to adequately wrap the muscle around the heartwith a satisfactory fit. Also, if adequate blood flow is not maintainedto the wrapped muscle, the muscle may necrose. The muscle may stretchafter wrapping reducing its constraining benefits and is generally notsusceptible to postoperative adjustment. Finally, the muscle may fibroseand adhere to the heart causing undesirable constraint on thecontraction of the heart during systole.

[0017] In addition to cardiomyoplasty, mechanical assist devices havebeen developed as intermediate procedures for treating congestive heartdisease. Such devices include left ventricular assist devices (“LVAD”)and total artificial hearts (“TAH”). An LVAD includes a mechanical pumpfor urging blood flow from the left ventricle and into the aorta. Anexample of such is shown in U.S. Pat. No. 4,995,857 to Arnold dated Feb.26, 1991. LVAD surgeries are still in U.S. clinical trials and notgenerally available. Such surgeries are expensive. The devices are atrisk of mechanical failure and frequently require external powersupplies. TAH devices, such as the celebrated Jarvik heart, are used astemporary measures while a patient awaits a donor heart for transplant.

[0018] Other attempts at cardiac assist devices are found in U.S. Pat.No. 4,957,477 to Lundback dated Sep. 18, 1990, U.S. Pat. No. 5,131,905to Grooters dated Jul. 21, 1992 and U.S. Pat. No. 5,256,132 to Snydersdated Oct. 26, 1993. Both of the Grooters and Snyders patents teachcardiac assist devices which pump fluid into chambers opposing the heartto assist systolic contractions of the heart. The Lundbäck patentteaches a double-walled jacket surrounding the heart. A fluid fills achamber between the walls of the jacket. The inner wall is positionedagainst the heart and is pliable to move with the heart. Movement of theheart during beating displaces fluid within the jacket chamber.

[0019] Commonly assigned U.S. Pat. No. 5,702,343 to Alferness dated Dec.30, 1997 teaches a jacket to constrain cardiac expansion duringdiastole. The present invention pertains to improvements to theinvention disclosed in the '343 patent.

II. SUMMARY OF THE INVENTION

[0020] According to a preferred embodiment of the present invention, amethod and device are disclosed for treating congestive heart diseaseand related cardiac complications such as valvular disorders. Theinvention includes a jacket of biologically compatible material. Thejacket has an internal volume dimensioned for an apex of the heart to beinserted into the volume and for the jacket to be slipped over theheart. The jacket has a longitudinal dimension between upper and lowerends sufficient for the jacket to surround a lower portion of the heartwith the jacket surrounding a valvular annulus of the heart and furthersurrounding the lower portion to cover at least the ventricular lowerextremities of the heart. The jacket is adapted to be secured to theheart with the jacket surrounding at least the valvular annulus and theventricular lower extremities. The jacket is adjustable on the heart tosnugly conform to an external geometry of the heart and assume a maximumadjusted volume for the jacket to constrain circumferential expansion ofthe heart beyond the maximum adjusted volume during diastole and topermit unimpeded contraction of the heart during systole. In oneembodiment, a lower end of the jacket can be secured to the patient'sdiaphragm after placement around the heart.

III. BRIEF DESCRIPTION OF THE DRAWINGS

[0021]FIG. 1 is a schematic cross-sectional view of a normal, healthyhuman heart shown during systole;

[0022]FIG. 1A is the view of FIG. 1 showing the heart during diastole;

[0023]FIG. 1B is a view of a left ventricle of a healthy heart as viewedfrom a septum and showing a mitral valve;

[0024]FIG. 2 is a schematic cross-sectional view of a diseased humanheart shown during systole;

[0025]FIG. 2A is the view of FIG. 2 showing the heart during diastole;

[0026]FIG. 2B is the view of FIG. 1B showing a diseased heart;

[0027]FIG. 3 is a perspective view of a first embodiment of a cardiacconstraint device according to the present invention;

[0028]FIG. 3A is a side elevation view of a diseased heart in diastolewith the device of FIG. 3 in place;

[0029]FIG. 4 is a perspective view of a second embodiment of a cardiacconstraint device according to the present invention;

[0030]FIG. 4A is a side elevation view of a diseased heart in diastolewith the device of FIG. 4 in place;

[0031]FIG. 5 is a cross-sectional view of a device of the presentinvention overlying a myocardium and with the material of the devicegathered for a snug fit;

[0032]FIG. 6 is an enlarged view of a knit construction of the device ofthe present invention in a rest state; and

[0033]FIG. 7 is a schematic view of the material of FIG. 6.

IV. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] With initial reference to FIGS. 1 and 1A, a normal, healthy humanheart H′ is schematically shown in cross-section and will now bedescribed in order to facilitate an understanding of the presentinvention. In FIG. 1, the heart H′ is shown during systole (i.e., highleft ventricular pressure). In FIG. 1A, the heart H′ is shown duringdiastole (i.e., low left ventricular pressure).

[0035] The heart H′ is a muscle having an outer wall or myocardium MYO′and an internal wall or septum S′. The myocardium MYO′ and septum S′define four internal heart chambers including a right atrium RA′, a leftatrium LA′, a right ventricle RV′ and a left ventricle LV′. The heart H′has a length measured along a longitudinal axis AA′ BB′ from an upperend or base B′ to a lower end or apex A′.

[0036] The right and left atria RA′, LA′ reside in an upper portion UP′of the heart H′ adjacent the base B′. The right and left ventricles RV′,LV′ reside in a lower portion LP′ of the heart H′ adjacent the apex A′.The ventricles RV′, LV′ terminate at ventricular lower extremities LE′adjacent the apex A′ and spaced therefrom by the thickness of themyocardium MYO′.

[0037] Due to the compound curves of the upper and lower portions UP′,LP′, the upper and lower portions UP′, LP′ meet at a circumferentialgroove commonly referred to as the A-V groove AVG′. Extending away fromthe upper portion UP′ are a plurality of major blood vesselscommunicating with the chambers RA′, RV′, LA′, LV′. For ease ofillustration, only the superior vena cava SVC′ and a left pulmonary veinLPV′ are shown as being representative.

[0038] The heart H′ contains valves to regulate blood flow between thechambers RA′, RV′, LA′, LV′ and between the chambers and the majorvessels (e.g., the superior vena cava SVC′ and a left pulmonary veinLPV′). For ease of illustration, not all of such valves are shown.Instead, only the tricuspid valve TV′ between the right atrium RA′ andright ventricle RV′ and the mitral valve MV′ between the left atrium LA′and left ventricle LV′ are shown as being representative.

[0039] The valves are secured, in part, to the myocardium MYO′ in aregion of the lower portion LP′ adjacent the A-V groove AVG′ andreferred to as the valvular annulus VA′. The valves TV′ and MV′ open andclose through the beating cycle of the heart H.

[0040]FIGS. 1 and 1A show a normal, healthy heart H′ during systole anddiastole, respectively. During systole (FIG. 1), the myocardium MYO′ iscontracting and the heart assumes a shape including a generally conicallower portion LP′. During diastole (FIG. 1A), the heart H′ is expandingand the conical shape of the lower portion LP′ bulges radially outwardly(relative to axis AA′-BB′).

[0041] The motion of the heart H′ and the variation in the shape of theheart H′ during contraction and expansion is complex. The amount ofmotion varies considerably throughout the heart H′. The motion includesa component which is parallel to the axis AA′-BB′ (conveniently referredto as longitudinal expansion or contraction). The motion also includes acomponent perpendicular to the axis AA′-BB′ (conveniently referred to ascircumferential expansion or contraction).

[0042] Having described a healthy heart H′ during systole (FIG. 1) anddiastole (FIG. 1A), comparison can now be made with a heart deformed bycongestive heart disease. Such a heart H is shown in systole in FIG. 2and in diastole in FIG. 2A. All elements of diseased heart H are labeledidentically with similar elements of healthy heart H′ except only forthe omission of the apostrophe in order to distinguish diseased heart Hfrom healthy heart H′.

[0043] Comparing FIGS. 1 and 2 (showing hearts H′ and H during systole),the lower portion LP of the diseased heart H has lost the taperedconical shape of the lower portion LP′ of the healthy heart H′. Instead,the lower portion LP of the diseased heart H bulges outwardly betweenthe apex A and the A-V groove AVG. So deformed, the diseased heart Hduring systole (FIG. 2) resembles the healthy heart H′ during diastole(FIG. 1A). During diastole (FIG. 2A), the deformation is even moreextreme.

[0044] As a diseased heart H enlarges from the representation of FIGS. 1and 1A to that of FIGS. 2 and 2A, the heart H becomes a progressivelyinefficient pump. Therefore, the heart H requires more energy to pumpthe same amount of blood. Continued progression of the disease resultsin the heart H being unable to supply adequate blood to the patient'sbody and the patient becomes symptomatic insufficiency.

[0045] For ease of illustration, the progression of congestive heartdisease has been illustrated and described with reference to aprogressive enlargement of the lower portion LP of the heart H. Whilesuch enlargement of the lower portion LP is most common and troublesome,enlargement of the upper portion UP may also occur.

[0046] In addition to cardiac insufficiency, the enlargement of theheart H can lead to valvular disorders. As the circumference of thevalvular annulus VA increases, the leaflets of the valves TV and MV mayspread apart. After a certain amount of enlargement, the spreading maybe so severe the leaflets cannot completely close (as illustrated by themitral valve MV in FIG. 2A). Incomplete closure results in valvularregurgitation contributing to an additional degradation in cardiacperformance. While circumferential enlargement of the valvular annulusVA may contribute to valvular dysfunction as described, the separationof the valve leaflets is most commonly attributed to deformation of thegeometry of the heart H. This is best described with reference to FIGS.1B and 2B.

[0047]FIGS. 1B and 2B show a healthy and diseased heart, respectively,left ventricle LV′, LV during systole as viewed from the septum (notshown in FIGS. 1B and 2B). In a healthy heart H′, the leaflets MVL′ ofthe mitral valve MV′ are urged closed by left ventricular pressure. Thepapillary muscles PM′, PM are connected to the heart wall MYO′, MYO,near the lower ventricular extremities LE′, LE. The papillary musclesPM′, PM pull on the leaflets MVL′, MVL via connecting chordae tendineaeCT′, CT. Pull of the leaflets by the papillary muscles functions toprevent valve leakage in the normal heart by holding the valve leafletsin a closed position during systole. In the significantly diseased heartH, the leaflets of the mitral valve may not close sufficiently toprevent regurgitation of blood from the ventricle LV to the atriumduring systole.

[0048] As shown in FIG. 1B, the geometry of the healthy heart H′ is suchthat the myocardium MYO′, papillary muscles PM′ and chordae tendineaeCT′ cooperate to permit the mitral valve MV′ to fully close. However,when the myocardium MYO bulges outwardly in the diseased heart H (FIG.2B), the bulging results in displacement of the papillary muscles PM.This displacement acts to pull the leaflets MVL to a displaced positionsuch that the mitral valve cannot fully close.

[0049] Having described the characteristics and problems of congestiveheart disease, the treatment method and apparatus of the presentinvention will now be described.

[0050] In general, a jacket of the invention is configured to surroundthe myocardium MYO. As used herein, “surround” means that jacketprovides reduced expansion of the heart wall during diastole by applyingconstraining surfaces at least at diametrically opposing aspects of theheart. In some preferred embodiments disclosed herein, the diametricallyopposed surfaces are interconnected, for example, by a continuousmaterial that can substantially encircle the external surface of theheart.

[0051] With reference now to FIGS. 3, 3A, 4 and 4A, the device of thepresent invention is shown as a jacket 10 of flexible, biologicallycompatible material. The jacket 10 is an enclosed knit material havingupper and lower ends 12, 14. The jacket 10, 10′ defines an internalvolume 16, 16′ which is completely enclosed but for the open ends 12,12′ and 14′. In the embodiment of FIG. 3, lower end 14 is closed. In theembodiment of FIG. 4, lower end 14′ is open. In both embodiments, upperends 12, 12′ are open. Throughout this description, the embodiment ofFIG. 3 will be discussed. Elements in common between the embodiments ofFIGS. 3 and 4 are numbered identically with the addition of anapostrophe to distinguish the second embodiment and such elements neednot be separately discussed.

[0052] The jacket 10 is dimensioned with respect to a heart H to betreated. Specifically, the jacket 10 is sized for the heart H to beconstrained within the volume 16. The jacket 10 can be slipped aroundthe heart H. The jacket 10 has a length L between the upper and lowerends 12, 14 sufficient for the jacket 10 to constrain the lower portionLP. The upper end 12 of the jacket 10 extends at least to the valvularannulus VA and further extends to the lower portion LP to constrain atleast the lower ventricular extremities LE.

[0053] Since enlargement of the lower portion LP is most troublesome, ina preferred embodiment, the jacket 10 is sized so that the upper end 12can reside in the A-V groove AVG. Where it is desired to constrainenlargement of the upper portion UP, the jacket 10 may be extended tocover the upper portion UP.

[0054] Sizing the jacket 10 for the upper end 12 to terminate at the A-Vgroove AVG is desirable for a number of reasons. First, the groove AVGis a readily identifiable anatomical feature to assist a surgeon inplacing the jacket 10. By placing the upper end 12 in the A-V grooveAVG, the surgeon is assured the jacket 10 will provide sufficientconstraint at the valvular annulus VA. The A-V groove AVG and the majorvessels act as natural stops for placement of the jacket 10 whileassuring coverage of the valvular annulus VA. Using such features asnatural stops is particularly beneficial in minimally invasive surgerieswhere a surgeon's vision may be obscured or limited.

[0055] When the parietal pericardium is opened, the lower portion LP isfree of obstructions for applying the jacket 10 over the apex A. If,however, the parietal pericardium is intact, the diaphragmaticattachment to the parietal pericardium inhibits application of thejacket over the apex A of the heart . In this situation, the jacket canbe opened along a line extending from the upper end 12′ to the lower end14′ of jacket 10′. The jacket can then be applied around the pericardialsurface of the heart and the opposing edges of the opened line securedtogether after placed on the heart. Systems for securing the opposingedges are disclosed in, for example, U.S. Pat. No. 5,702,343, the entiredisclosure of which is incorporated herein by reference. The lower end14′ can then be secured to the diaphragm or associated tissues using,for example, sutures, staples, etc.

[0056] In the embodiment of FIGS. 3 and 3A, the lower end 14 is closedand the length L is sized for the apex A of the heart H to be receivedwithin the lower end 14 when the upper end 12 is placed at the A-Vgroove AVG. In the embodiment of FIGS. 4 and 4A, the lower end 14′ isopen and the length L′ is sized for the apex A of the heart H toprotrude beyond the lower end 14′ when the upper end 12′ is placed atthe A-V groove AVG. The length L′ is sized so that the lower end 14′extends beyond the lower ventricular extremities LE such that in both ofjackets 10, 10′, the myocardium MYO surrounding the ventricles RV, LV isin direct opposition to material of the jacket 10, 10′. Such placementis desirable for the jacket 10, 10′ to present a constraint againstenlargement of the ventricular walls of the heart H.

[0057] After the jacket 10 is positioned on the heart H as describedabove, the jacket 10 is secured to the heart. Preferably, the jacket 10is secured to the heart H through sutures. The jacket 10 is sutured tothe heart H at suture locations S circumferentially spaced along theupper end 12. While a surgeon may elect to add additional suturelocations to prevent shifting of the jacket 10 after placement, thenumber of such locations S is preferably limited so that the jacket 10does not restrict contraction of the heart H during systole.

[0058] To permit the jacket 10 to be easily placed on the heart H, thevolume and shape of the jacket 10 are larger than the lower portion LPduring diastole. So sized, the jacket 10 may be easily slipped aroundthe heart H. Once placed, the jacket's volume and shape are adjusted forthe jacket 10 to snugly conform to the external geometry of the heart Hduring diastole. Such sizing is easily accomplished due to the knitconstruction of the jacket 10. For example, excess material of thejacket 10 can be gathered and sutured S″ (FIG. 5) to reduce the volumeof the jacket 10 and conform the jacket 10 to the shape of the heart Hduring diastole. Such shape represents a maximum adjusted volume. Thejacket 10 constrains enlargement of the heart H beyond the maximumadjusted volume while preventing restricted contraction of the heart Hduring systole. As an alternative to gathering of FIG. 5, the jacket 10can be provided with other ways of adjusting volume. For example, asdisclosed in U.S. Pat. No. 5,702,343, the jacket can be provided with aslot. The edges of the slot can be drawn together to reduce the volumeof the jacket.

[0059] The jacket 10 is adjusted to a snug fit on the heart H duringdiastole. Care is taken to avoid tightening the jacket 10 too much suchthat cardiac function is impaired. During diastole, the left ventricleLV fills with blood. If the jacket 10 is too tight, the left ventricleLV cannot adequately expand and left ventricular pressure will rise.During the fitting of the jacket 10, the surgeon can monitor leftventricular pressure. For example, a well-known technique for monitoringso-called pulmonary wedge pressure uses a catheter placed in thepulmonary artery. The wedge pressure provides an indication of fillingpressure in the left atrium LA and left ventricle LV. While minorincreases in pressure (e.g., 2-3 mm Hg) can be tolerated, the jacket 10is snugly fit on the heart H but not so tight as to cause a significantincrease in left ventricular pressure during diastole.

[0060] As mentioned, the jacket 10 is constructed from a knit,biocompatible material. The knit 18 is illustrated in FIG. 6.Preferably, the knit is a so-called “Atlas knit” well known in thefabric industry. The Atlas knit is described in Paling, Warp KnittingTechnology, p. 111, Columbine Press (Publishers) Ltd., Buxton, GreatBritain (1970).

[0061] The Atlas knit is a knit of fibers 20 having directionalexpansion properties. More specifically, the knit 18, although formed ofgenerally inelastic fibers 20, permits a construction of a flexiblefabric at least slightly expandable beyond a rest state. FIG. 6illustrates the knit 18 in a rest state. The fibers 20 of the fabric 18are woven into two sets of fiber strands 21 a, 21 b having longitudinalaxes X_(a) and X_(b). The strands 21 a, 21 b are interwoven to form thefabric 18 with strands 21 a generally parallel and spaced-apart and withstrands 21 b generally parallel and spaced-apart.

[0062] For ease of illustration, fabric 18 is schematically shown inFIG. 7 with the axis of the strands 21 a, 21 b only being shown. Thestrands 21 a, 21 b are interwoven with the axes X_(a) and X_(b) defininga diamond-shaped open cell 23 having diagonal axes A. In a preferredembodiment, the axes A_(m) are 5 mm in length when the fabric 18 is atrest and not stretched. The fabric 18 can stretch in response to aforce. For any given force, the fabric 18 stretches most when the forceis applied parallel to the diagonal axes A_(m). The fabric 18 stretchesleast when the force is applied parallel to the strand axes X_(a) andX_(b). The jacket 10 is constructed for the material of the knit to bedirectionally aligned for a diagonal axis A_(m) to be parallel to theheart's longitudinal axis AA-BB

[0063] While the jacket 10 is expandable due to the above described knitpattern, the fibers 20 of the knit 18 are preferably non-expandable.While all materials expand to at least a small amount, the fibers 20 arepreferably formed of a material with a low modulus of elasticity. Inresponse to the low pressures in the heart H during diastole, the fibers20 are non-elastic. In a preferred embodiment, the fibers are 70 Denierpolyester. While polyester is presently preferred, other suitablematerials include polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE),polypropylene and stainless steel.

[0064] The knit material has numerous advantages. Such a material isflexible to permit unrestricted movement of the heart H (other than thedesired constraint on circumferential expansion). The material is opendefining a plurality of interstitial spaces for fluid permeability aswell as minimizing the amount of surface area of direct contact betweenthe heart H and the material of the jacket 10 (thereby minimizing areasof irritation or abrasion) to minimize fibrosis and scar tissue.

[0065] The open areas of the knit construction also allows forelectrical connection between the heart and surrounding tissue forpassage of electrical current to and from the heart. For example,although the knit material is an electrical insulator, the open knitconstruction is sufficiently electrically permeable to permit the use oftrans-chest defibrillation of the heart. Also, the open, flexibleconstruction permits passage of electrical elements (e.g., pacer leads)through the jacket. Additionally, the open construction permits otherprocedures, e.g., coronary bypass, to be performed without removal ofthe jacket.

[0066] A large open area for cells 23 is desirable to minimize theamount of surface area of the heart H in contact with the material ofthe jacket 10 (thereby reducing fibrosis). However, if the cell area 23is too large, localized aneurysm can form. Also, a strand 21 a, 21 b canoverly a coronary vessel with sufficient force to partially block thevessel. A smaller cell size increases the number of strands therebydecreasing the restricting force per strand. Preferably, a maximum cellarea is no greater than about 6.45 Cm² (about 2.54 cm by 2.54 cm) and,more preferably, is about 0.25 cm² (about 0.5 cm by 0.5 cm). The maximumcell area is the area of a cell 23 after the material of the jacket 10is fully stretched and adjusted to the maximum adjusted volume on theheart H as previously described.

[0067] The fabric 18 is preferably tear and run resistant. In the eventof a material defect or inadvertent tear, such a defect or tear isrestricted from propagation by reason of the knit construction.

[0068] With the foregoing, a device and method have been taught to treatcardiac disease. The jacket 10 constrains further undesirablecircumferential enlargement of the heart while not impeding other motionof the heart H. With the benefits of the present teachings, numerousmodifications are possible. For example, the jacket 10 need not bedirectly applied to the epicardium (i.e., outer surface of themyocardium) but could be placed over the parietal pericardium. Further,an anti-fibrosis lining (such as a PTFE coating on the fibers of theknit) could be placed between the heart H and the jacket 10.Alternatively, the fibers 20 can be coated with PTFE.

[0069] The jacket 10 is low-cost, easy to place and secure, and issusceptible to use in minimally invasive procedures. The thin, flexiblefabric 18 permits the jacket 10 to be collapsed and passed through asmall diameter tube in a minimally invasive procedure.

[0070] The jacket 10 can be used in early stages of congestive heartdisease. For patients facing heart enlargement due to viral infection,the jacket 10 permits constraint of the heart H for a sufficient time topermit the viral infection to pass. In addition to preventing furtherheart enlargement, the jacket 10 treats valvular disorders byconstraining circumferential enlargement of the valvular annulus anddeformation of the ventricular walls.

[0071] The jacket 10, including the knit construction, freely permitslongitudinal and circumferential contraction of the heart H (necessaryfor heart function). Unlike a solid wrap (such as a muscle wrap in acardiomyoplasty procedure), the fabric 18 does not impede cardiaccontraction. After fitting, the jacket 10 is inelastic to preventfurther heart enlargement while permitting unrestricted inward movementof the ventricular walls. The open cell structure permits access tocoronary vessels for bypass procedures subsequent to placement of thejacket 10. Also, in cardiomyoplasty, the latissimus dorsi muscle has avariable and large thickness (ranging from about 1 mm to 1 cm). Thematerial of the jacket 10 is uniformly thin (less than 1 mm thick). Thethin wall construction is less susceptible to fibrosis and minimizesinterference with cardiac contractile function.

[0072] Animal test studies on the device show the efficacy of theinvention. Test animals were provided with the device 10 of FIG. 3. Theanimals' hearts were rapidly paced to induce enlargement. After sixweeks, animals without the device experienced significant heartenlargement while those with the device experienced no significantenlargement. Further, animals with the device had significantly reducedmitral valve regurgitation.

[0073] In addition to the foregoing, the present invention can be usedto reduce heart size at the time of placement in addition to preventingfurther enlargement. For example, the device can be placed on the heartand sized snugly to urge the heart to a reduced size.

[0074] More preferably, the heart size can be reduced at the time ofjacket placement through drugs (e.g., dobutamine, dopamine orepinephrine or any other positive inotropic agents) to reduce the heartsize. The jacket of the present invention is then snugly placed on thereduced sized heart and prevents enlargement beyond the reduced size.

[0075] From the foregoing, a low cost, reduced risk method and deviceare taught to treat cardiac disease. The invention is adapted for usewith both early and later stage congestive heart disease patients. Theinvention reduces the enlargement rate of the heart as well as reducingcardiac valve regurgitation.

What is claimed is:
 1. A device for treating cardiac disease of a hearthaving a longitudinal axis from an apex to a base and having an upperportion and a lower portion divided by an A-V groove, said heartincluding a valvular annulus adjacent said A-V groove and ventricularlower extremities adjacent said apex, the device comprising: a jacket offlexible material of knit construction defining a volume between an openupper end and a lower end, said jacket dimensioned for said apex of saidheart to be inserted into said volume through said open upper end andfor said jacket to be slipped over said heart, said jacket furtherdimensioned for said jacket to have a longitudinal dimension betweensaid upper and lower ends sufficient for said jacket to constrain saidlower portion with said jacket constraining said valvular annulus andfurther constraining said ventricular lower extremities; said jacketadapted to be secured to said heart with said jacket having portionsdisposed on opposite sides of the heart between said valvular annulusand said ventricular lower extremities; and said jacket adapted to beadjusted on said heart to snugly conform to an external geometry of saidheart and assume a maximum adjusted volume for said jacket to constraincircumferential expansion of said heart beyond said maximum adjustedvolume during diastole and permit substantially unimpeded contraction ofsaid heart during systole.
 2. A device according to claim 2 wherein:said material is expandable along a first material axis in response to aforce parallel to said first axis greater than an expansion of saidmaterial along a second axis in response to a force of equal magnitudeparallel to said second axis; said material oriented for said first axisto extend circumferentially around said longitudinal dimension.
 3. Adevice according to claim 1 wherein said jacket is open at said lowerend.
 4. A device according to claim 1 wherein said jacket is closed atsaid lower end.
 5. A device according to claim 1 wherein said materialis run resistant.
 6. A device according to claim 5 wherein: saidmaterial is expandable along a first material axis in response to aforce parallel to said first axis greater than an expansion of saidmaterial along a perpendicular second axis in response to a force ofequal magnitude parallel to said second axis; said material oriented forsaid first axis to extend from said upper end of said jacket toward saidlower end.
 7. A device according to claim 1 wherein said material issufficiently flexible to gather excess amounts of said materialfollowing placement of said jacket over said heart to snugly conformsaid material to an external geometry of said heart.
 8. A deviceaccording to claim 5 wherein said material is sufficiently flexible togather excess amounts of said material following placement of saidjacket over said heart to snugly conform said material to an externalgeometry of said heart.
 9. A device according to claim 1 wherein saidmaterial is selected from a group of polytetrafluoroethylene, expandedpolytetrafluoroethylene, polypropylene, polyester or stainless steel.10. A device according to claim 5 wherein said material is formed ofelongated fibers selected from a group of polytetrafluoroethylene,expanded polytetrafluoroethylene, polypropylene, polyester or stainlesssteel.
 11. A device according to claim 1 wherein said jacket is sized toat least partially cover and constrain said upper portion.
 12. A deviceaccording to claim 1 further comprising a liner sized and positioned tobe disposed between said heart and said jacket, said liner formed of anantifibrotic material.
 13. A device according to claim 1 wherein thejacket is electrically permeable.
 14. A device for treating cardiacdisease of a heart having a longitudinal axis from an apex to a base andhaving an upper portion and a lower portion divided by an A-V groove,said heart including a valvular annulus adjacent said A-V groove andventricular lower extremities adjacent said apex, the device comprising:a jacket of flexible, electrically permeable material adapted to besecured to said heart with said jacket having portions disposed onopposite sides of the heart between said valvular annulus and saidventricular lower extremities; and said jacket adapted to be adjusted onsaid heart to snugly conform to an external geometry of said heart andassume a maximum adjusted volume for said jacket to constraincircumferential expansion of said heart beyond said maximum adjustedvolume during diastole and permit unimpeded contraction of said heartduring systole.
 15. A device according to claim 2 wherein said jacketcircumferentially surrounds said heart.
 16. A method for treatingcardiac disease of a patient's heart, said method comprising: surgicallyaccessing said patient's heart and diaphragm; placing a jacket aroundsaid heart, said jacket Comprising a biomedical material having an upperend and a lower end; adjusting said jacket on said heart to snuglyconform to an external geometry of said heart and assume a maximumadjusted volume for said jacket to constrain circumferential expansionof said heart beyond said maximum adjusted volume during diastole andpermitting unimpeded contraction of said heart during systole; andsecuring said lower end of said jacket to said diaphragm.
 17. A methodaccording to claim 16 wherein said lower end of said jacket is securedto said diaphragm using sutures.